An antimicrobial composition and a method of producing an antimicrobial composition

Abstract: The invention provides an antimicrobial composition of matter comprising a dry distillate of at least one plant other than beefsteak plant, bamboo, ginger, mugwort and garlic. The invention further provides shaped articles containing or carrying the composition of matter and a method of producing the same composition of matter.

Description: FIELD OF THE INVENTION This invention relates to an antimicrobial food product containing an antimicrobial composition comprising a dry distillate of specific plants. BACKGROUND OF THE INVENTION It is known that aqueous and organic extracts of certain plants including ginger, bamboo grass, mugwort, etc. contain antimicrobially active principles. By way of illustration, Japanese Patent Kokai No. 32705/1985 discloses an antimicrobial composition containing a ginger rhizome extract as an active ingredient. Derived from naturally-occurring sources, namely plants, such antimicrobial substances are safe and expected to find application in the field of food and cosmetic additive ingredients, among others. Moreover, though unrelated to antimicrobial use, Japanese Patent Publication No. 8694/1986 describes a deodorant composition containing a dry distillate of tea leaf boiling between 180 and 200°C at 20 mmHg, for instance. GB-A-1 300 966 discloses a composition comprising a dry distillate of at least one plant such as pearl barley, unpolished rice, low striped bamboo, yewtree, mugwort, boxthorn, leaves of arrow root, red pepper and buries of boxthorn. However, this document does not disclose dry distillates of rooibos tea, Guinea pepper, sesame and parsley nor an antimicrobial food product containing an antimicrobial composition comprising a dry distillate of these plants. JP-A-04341169 discloses a preservative for food containing Guinea pepper extract as an active ingredient which is obtained by aqueous solvent extraction. However, this document does not disclose dry distillation of Guinea pepper nor an antimicrobial food product containing an antimicrobial composition comprising dry distillates of rooibos tea, Guinea pepper, sesame and/or parsley. While antimicrobial agents extracted from plants are generally more desirable than synthetic preservatives and synthetic antimicrobial agents as far as safety is concerned, they are usually less active than the synthetic substances. Moreover, because of the characteristic odor, taste and color which trace back to the source plant, a natural substance is often considered unacceptable for food or cosmetic use. Furthermore, the extraction process required is not only time-consuming but entails a complicated after-treatment. The inventor of this invention having done an extensive exploration into antimicrobial substances occurring in plants arrived at the assumption that antimicrobial substances in situ , namely in plants, are mostly in a masked state as its functional groups intrinsic to antimicrobial activity are bound to each other to form a condensate or polymer and such condensed or polymerized substance, if extracted, would not fully deploy its antimicrobial potential. Starting from that assumption, the inventor did further research and developed this invention. The object of this invention is to provide an antimicrobial food composition containing an antimicrobial composition of matter having high antimicrobial activity and substantially free of the characteristic odor, taste and color of the source plant. SUMMARY OF THE INVENTION The antimicrobial composition of matter according to this invention is a dry distillate of at least one plant selected from the group consisting of rooibos tea, Guinea Pepper, sesame, and parsley. In accordance with this invention, one or more plants as defined above, are used as the source plants. Since the use of beefsteak plant, bamboo, ginger, mugwort and/or garlic gives antimicrobial compositions of matter having particularly high activity, the invention involving the use of these specific plants is described in a copending application and is, therefore, excluded from the instant application. The plant, either the whole or a part thereof, is crushed and dried, if necessary, and subjected to dry distillation to provide the objective antimicrobial composition of matter. This dry distillation is carried out at high temperature and under reduced pressure. The typical conditions of dry distillation are 130 - 220°C and more desirably 140 - 210°C, and 10 - 50 mmHg, and especially 15 - 40 mmHg. If the temperature is too low, the necessary pyrolysis does not proceed to a satisfactory extent, while too high a distillation temperature results in excessive carbonization and a reduced yield. On the other hand, if the degree of vacuum is insufficient, the yield of the desired distillate will be decreased. The initial fraction of the distillate may be cut off. The dry distillate thus obtained is usually a viscous fluid but for the ease of handling, it can be diluted with water, ethanol, propylene glycol or the like. The dry distillate may also be further purified. The activity of the antimicrobial composition of matter obtained by the above procedure is specific to the source plant. Therefore, to obtain an extended antimicrobial spectrum, it is preferable that two or more different plants be subjected together to dry distillation or dry distillates from two or more different plants be used in admixture. Moreover, the dry distillate from any of said plants may be used in combination with other antimicrobial substances. The antimicrobial composition of matter obtainable by the above dry distillation procedure is used to prepare the food product of the present invention. Thus, the term "antimicrobial composition of matter" is used herein to mean any antimicrobially active material whether it can be more properly termed for example an antibacterial agent, antifungal agent, bacteriostatic agent, antiseptic or preservative. It is suspected that generally the antimicrobial substances in plants are partly present in the free form but mostly in the form of complexes formed as their functional groups pertinent to antimicrobial activity are bound to each other by condensation or polymerization. Therefore, mere extraction of them with water or an organic solvent leaves such complexes intact so that the antimicrobially active functional groups remain masked. Therefore, extracts of plants are lean in the free form of active substances and accordingly show only moderate activity. In the method of this invention, however, the plant tissue is exposed to the high-temperature and vacuum conditions of dry distillation, with the result that the above-mentioned complexes are thermally decomposed to unmask the antimicrobially active functional groups and, hence, the distillates are rich in the active substances. Thus, the dry distillation according to this invention not only serves to thermally decompose said complexes but also enables fractional recovery of the antimicrobial composition of matter. EXAMPLES The following examples are intended to describe this invention in further detail. Examples 1 - 4 Using rooibos tea (Example 1), guinea pepper (Example 2) sesame (Example 3) and parsley (Example 4) sample were prepared as follows. The plants were dried and antimicrobial principles were separated from the materials by the following three methods. (1) A dry distillation equipment was charged with 200 g of previously dried plants and the load was dry-distilled at a temperature of about 200°C and a reduced pressure of about 35 mmHg. The distillate was recovered in 1500 ml of ethanol. (2) Twenty (20) grams of previously dried plants were extracted with 150 g of boiling water. (3) Twenty (20) grams of previously dried plants were extracted with 150 g of hot ethanol. Compared with the samples obtained by methods (2) and (3), the samples obtained by method (1) were remarkably pale in color and suppressed in odor. Using each of the above samples obtained according to (1), (2) and (3), antimicrobial activity assays were carried out by the following two methods A and B. Method A Culture dishes, 90 mm in diameter, were each filled with 1 ml of the sample and 10 ml of sterilized agar medium, and after mixing, the agar was allowed to solidify. The resulting media were inoculated with 0.5 ml portions of Aspergillus niger , Escherichia coli or Staphylococcus aureus suspensions, respectively, and incubated at 35°C for 48 hours. Then, the growth of each microorganism was investigated. As to the bacteria, a loopful of the medium was sampled after incubation and inoculated onto an agar slant for the verification of growth. The media used was GP agar for the fungus and SCD medium for E . Coli and Sta . aureus . Method B Culture dishes, 90 mm in diameter, were each filled with 10 ml of sterilized agar medium and the agar was allowed to cool and solidify. The resulting media were inoculated with 0.5 ml portions of Asp . niger , E . coli and Sta . aureus suspensions. Separately, 0.1 ml of each sample was dripped on a paper disk, 10 mm in diameter, and allowed to stand at room temperature for 1 hour to dry. This drying procedure of short duration was intended to prevent diffusion of the sample. The dried disk was then placed on the inoculated medium and incubated at 35°C for 48 hours to check for the growth of the microorganism. The medium used was GP agar for the fungus and SCD medium for E . coli and Sta . aureus . In method A, the results were evaluated according to the following criteria. Fungus - : Growth is found in entire area + : No growth in less than 50% of area ++ : No growth in 50% or more of area +++ : No growth at all Bacteria - : Colonies are found in entire area + : No colonies in less than 50% of area ++ : No colonies in 50% or more of area +++ : No colonies at all The growth on the slant medium was evaluated on the two-stage scale of o (no growth) and x (growth). In method B, the following evaluation criteria were used. Fungus - : Growth is found on entire disk + : No growth on part of disk ++ : No growth on disk +++ : A zone of inhibition is found Bacteria - : No zone of inhibition around disk ± : A zone of inhibition within 1 mm from periphery of disk + : A zone of inhibition within 5 mm from periphery of disk ++ : A zone of inhibition beyond 5 mm from periphery of disk The data obtained by method A are shown in Table 1 and those obtained by method B in Table 2. The results of blank tests using ethanol alone are also shown as controls in Tables 1 and 2. Compared with the aqueous and ethanol extracts, the dry distillates were by far pale in color and suppressed in odor. Plant Asp. niger E. Coli Sta. aureus Rooibos tea Dry distillate ++ ++/x +++/o Aqueous extract + - /x - /x Ethanol extract + - /x - /x Guinea pepper Dry distillate + + /x +++/o Aqueous extract - - /x - /x Ethanol extract + - /x - /x Sesame Dry distillate + + /x - /x Aqueous extract - - /x - /x Ethanol extract - + /x - /x Parsley Dry distillate ++ - /x + /x Aqueous extract ++ - /x + /x Ethanol extract - +++/x - /x Control (Ethanol) + or - - or +/x - /x Plant Asp. niger E. Coli Sta. aureus Rooibos tea Dry distillate ± ± ++ Aqueous extract - - - Ethanol extract - - - Guinea pepper Dry distillate ± - - Aqueous extract - - - Ethanol extract - - - Sesame Dry distillate + + - Aqueous extract ± - - Ethanol extract - - - Parsley Dry distillate ± + ± Aqueous extract ± - - Ethanol extract ± - - Control (Ethanol) - or ± - - Example 5 The dry distillates, aqueous extracts and ethanol extracts of Rooibos tea, Guinea pepper, sesame and parsley used in the foregoing examples were respectively added to rice cake, bread dough, sausage and miso (bean paste) batches at the level of 1% by weight (inclusive of solvent). The respective food products were then prepared and their shelf-lives were investigated. Using the corresponding product not containing any of the additives as control, the activity of each antimicrobial additive was evaluated on the 3-grade scale of C (no change), B (effective) and A (very effective). The results are shown in Table 3. Rice cake Bread Sausage Miso Rooibos tea Dry distillate A ∼ B A ∼ B A A Aqueous extract B ∼ C C C C Ethanol extract B ∼ C C C C Guinea pepper Dry distillate B ∼ C B ∼ C A ∼ B B Aqueous extract C C C C Ethanol extract B ∼ C B ∼ C C C Sesame Dry distillate B ∼ C B ∼ C C B ∼ C Aqueous extract B ∼ C C C C Ethanol extract C C B ∼ C C Parsley Dry distillate B B ∼ C B ∼ C B ∼ C Aqueous extract B B ∼ C C C Ethanol extract C C B B ∼ C Thus, compared with the conventional aqueous and ethanol extracts of plants, the food products containing the antimicrobial compositions of matter according to this invention are remarkably higher in antimicrobial activity and less pronounced in odor, taste and color. Moreover, the method of this invention is advantageous in that since the necessary composition of matter can be obtained by mere dry distillation of the source plant, the production process is remarkably simple as compared with the conventional extraction procedure using water or an organic solvent.

Claims: An antimicrobial food product containing an antimicrobial composition of matter comprising a dry distillate of at least one plant selected from the group consisting of Rooibos tea, Guinea pepper, sesame, and parsley, wherein said dry distillate of plant is obtained by subjecting a plant to dry distillation under a reduced pressure of 10 to 50 mmHg at a temperature of 130 to 220 °C.

Inventors: FUKUNAGA TOSHIKAZU, FUKUNAGA, TOSHIKAZU
Applicants: ITOCHU FINE CHEMICAL CORP, SHIRAIMATSU SHINYAKU CO, ITOCHU FINE CHEMICAL CORPORATION, SHIRAIMATSU SHINYAKU KABUSHIKI KAISHA
Application year: 1994
Main classification: A01N65
IPC codes: A61K36, A01N65